Laptop computer inputting devices: effects on upper trapezius activity & perceived comfort

BackgroundThere is a trend indicating that laptop personal computers are replacing desktop computers at home and in the workplace. Although previousstudies have examined the effects of different types of external inputtingdevices, there is little evidence examining the effects of an external mouseversus integrated laptop touchpad inputting devices.AimTo compare Upper Trapezius (UT) muscle activity and levels of perceivedcomfort when using the integrated touchpad on a laptop personal computer (LPC) and a mouse inputting device.MethodsUtilising an experimental study design, 10 participants performed a 20-minute computer task on a LPC using both the integrated touchpad anda mouse inputting device. Bilateral surface electromyography (EMG) wasrecorded at four time periods (5, 10, 15 and 20 minutes). All EMG datawere normalised as a percentage of participants’ maximal voluntary contraction (%MVC). Additionally, a 10 centimetre visual analogue scale (VAS)was used to measure perceived comfort.ResultsMean UT muscle activity was 5.27%MVC and 8.08%MVC for the right andleft sides respectively when using the mouse. When using the touchpad,the levels were 14.72%MVC and 9.59%MVC for right and left sides, representing almost a threefold increase (p<0.05) for the right UT when computer tasking with the integrated touchpad compared to the mouse. LeftUT muscle activity levels were not significantly different (p>0.05) at anyof the four time periods when comparing the two devices. Furthermore,subjects perceived significantly less comfort (p=0.006) when computertasking with the integrated touchpad compared to the mouse, with meanVAS scores of 4.8 for the touchpad and 9.5 for the mouse (0 = discomfort, 10 = comfort).ConclusionsThe findings from this study provide evidence that computer tasking using the laptop’s integrated touchpad can result in adverse increases in UTmuscle activity compared to a mouse inputting device.